Vehicles: 34 single deck Scania KUB270 / Alexander Dennis Enviro 300SG buses plus up to 113 taxis
Station: Grid connected CNG with 2 compressors, high pressure gas cascade storage and 3 dispenser
Gas: CNG from grid (with Green Gas Certificates purchased from biomethane producers to offset CO2 emissions)
From September 2014 on, Reading's fleet of 34 CNG buses (biggest in the UK) have benefited from the new refuelling facilities built by Wärtsilä. This refuelling station is the first of its kind in the UK and will soon supply taxis, as well as buses, after Reading City Council received a grant of £368,750 to convert up to 113 conventional fuel-powered taxis into dual fuel vehicles. Taxi drivers will be able to freely access the refuelling facilities between 9am and 5pm, while usage between midnight and 7am must be previously arranged.
The current CNG Reading bus fleet adds to the existing 31 electric hybrid buses in the city, meaning 38% of the whole fleet is now labelled as "ultra-clean". The roof of the buses is equipped with 8 composite tanks that can contain up to 1200 litres of gas compressed above 214 bar. Natural gas powered vehicles produce less noise than their diesel/petrol counterparts, making them an ideal powertrain system for early morning operation, which is particularly interesting for an application such as urban buses. In terms of pollution reduction, CNG vehicles are reported to generate 80% less ozone forming emissions in comparison to gasoline fuelled vehicles. NOx emissions are reduced between 30 and 50% when compared to those of equivalent Euro V diesel buses.
CO2 emissions are not significantly reduced when using pure natural gas. In order to manage this drawback, the Gas Bus Alliance allows biogas producers to inject the same amount of bio-methane generated from agricultural sources into the gas mains, receiving several certificates that are sold to Reading Transport. This process is tracked and controlled by the Green Gas Certification Scheme, run by the Renewable Energy Association. Every litre of CNG taken from the mains to fill the bus tanks is replaced by a litre of biogas into the mains, allowing the vehicles to be classified as Low Carbon Emission Buses and providing the bus company with fiscal operating incentives.
Regarding costs, CNG buses are about 20% more expensive than diesel ones. However, the lower fuel costs make the investment worthwhile over a 10 year lifetime, even considering the new refilling infrastructure expenses. Moreover, in words of Mr Tony Pettitt, Reading Buses' Director of Resources, "Our natural gas buses are the most reliable vehicles in the fleet and we expect to continue to switch our fleet to CNG operation." This potential expansion in the future is corroborated by Kevin Robertson, General Manager Waste Water of Wärtsilä Ship Power: "Our service vans all run on CNG and as the infrastructure of refuelling facilities continues to expand, we expect to see this trend rapidly expanding in the coming years."